Mixing mill accumulating shelf



A ril 2, 1963 R. I. LUND MIXING MILL ACCUMULATING SHELF 2 Sheets-Sheet 1 Filed Feb. 8. 1962 INVENTOR. RICHARD I. LUND if April 2, 1963 R. I. LUND MIXING MILL ACCUMULATING SHELF 2 Sheets-sheaf 2 Filed Feb. 8, 1962 INVENTOR. RICHARD I. LUND ATTY.

United States Patent M 3,083,494 MIXING MILL ACQUMULATlNG SHELF Richard I. Lurid, Akron, Ohio, assignor to The B. F. Goodrich Company, New York, N.Y., a corporation of New York Fiied Feb. 3, 1962, Ser. No. 171,889 6 Ciaims. (Ci. 182) This invention pertains to apparatus for mixing plastic materials, and, more particularly, toimprovements in roll mills for the mixing of elastomeric materials.

In the mixing of elastomeric materials it is common practice to blend compounding ingredients into a rubber matrix-on a roll mill having a pair of closely adjustably spaced, horizontal, parallel and contra-rotating milling rolls. In such a mill, one of the rolls is rotated-at a higher speed than'the other, in the order of 40% greater, thereby subjecting material passing through the bight of such rolls to shearing forces which act to disperse the compounding ingredients uniformly throughout the rubber. The material passing'through the bight forms a'continuous band on one of the two rolls, generally the slower of'the two. The volume of the batch being mixed is preferably greater than that needed to form this band, and the excess material forms a rolling bank above the bight of the rolls. In order to more uniformly mix the batch and allow the bank to pass between the rolls the operator cuts the band from side to side with aknife held in his one hand, while rolling the material out with the other hand until the rolling bank is nearly completely passed between the rolls, at which time he allows the roll he has formed by hand to be caught in the bight to again form a band. At best, this operation is difiicult, time consuming and extremely dangerous to the operator.

In order to facilitate the mixing of the'band from side to side such mills have been furnished with overhead mixers comprising a pair of rollslocated above the mill rolls and parallelthe'reto. One of'these rolls is driven in timed relationship to 'the speed of the mill rolls. The operator can cut the entire band from its mill roll and throw it up to the bight of the overhead mixing rolls which pull the entire band up and dump it into the bight of the mill rolls. This, in'effect, lengthens the band of rubber, thereby reducing the size of the rolling'bank over the mill rolls. In addition, a guide carriage is provided in front of the overhead mixing rolls. This carriage travels in directions parallel'to the axes ofth'e rolls on an endless double reversing screw rotated in timed relationship to the rotational speed of the mill rolls. The carriage guides the rubber band to the overhead mixer rolls and automatically performs an operation similar to that of the operator in cutting the band from side to side.

In the use of'such equipment, particularly in conjunction with internal mixers of the Banbury type, where the size of the batch being-mixed is large,in'the order of 400 pounds or more, it isimpossible to completely eliminate the rolling bank of material above the mill rolls bight. The band of material being carried to the bight of the mill rolls by the overhead rolls tends to pass under this rolling bank and through the bight of the mill rolls again. Therefore, the material in the rolling bank does not become intimately mixed with the rest of the material with the result that the rest of the material is continually passed between the mill rolls to become overheated and possibly scorched or otherwise have its properties deteriorated.

In an effort to overcome'this'serious drawback in the milling of large rubber batches it became encumbent upon those concerned with the problem'to devise an apparatus which would insure complete and'intimate mixing of all portions of a batch being mixed thereon.

It is an object of this invention therefore, to provide an 3,683,404 Patented Apr. 2, 196-3 apparatus in combination'with a roll mill having an overhead mixer whereby all portions of an elastomeric batch being mixed on said mill are intimately mixed with one another.

It is a further objectof this invention to provide an apparatus'in combination with a roll mill having an'ove'rhead mixer wherein means are provided to accumulate a portion of an elastomeric batch being mixed thereon above and out of contact with the rollers of said mill before allowing said portion to pass between'said rolls.

It is a still further object of'this invention to provide an apparatus as described in the preceding paragraph wherein said means to accumulate a portion of the batch comprises a horizontal batch accumulating shelf mounted beneath the overhead mixer for'movementin-horizontal directions.

It is a still further object of the present invention to provide an apparatus as-described in the preceding paragraph wherein the'horizontal movement of s'aidshelf is effected in timedrelationship to the speed of rotation of the overhead mixing rolls.

Further objects and advantages to be gained'through the use of the present'invention will be apparent to those skilled in the art to which it pertains from the following detailed description of a preferred embodiment of the apparatus and from the drawings which form a part of this-application and in which:

FIG. 1 is a front elevational view of a rollmill with overhead mixer in combination with the movable 'stock accumulating shelf;

FIG. 2 is a cross-sectional side elevational View of the apparatus taken alongline 2- 2 of FIG. 1; and

'FIG. 3 is a schematic diagram'of the electrical and pneumatic circuits for controlling movement of the stock accumulating shelf.

The stock accumulating shelf assembly A of the present invention is illustrated in'the drawings as it is used in conjunction with a conventional two-roll mixing mill B, fitted with an overhead mixer C. The-mill B c-omprises'a pair of vertical side supports 10 in which a pair of milling rolls 11 and 12, having supporting shafts 13'and 13a, are journalled. A spur gear 14 is mounted onone end of shaft 13 for roll '11 and is engaged with a similar gear 15-mountedon the shaft '13:: for roll 12. A third spur gear 16, mounted on a drive shaft 17, is in driving engagement with gear 14, thus causing rolls 1'1 and 12 to rotate in'opposite directions as drive shaft -17, connected to a source of power not shown, is rotated. When rotated as shown in the drawings, the rolls 11 andl z draw a band 18 of elastomeric material from a rolling bank 19 of the material through the bight of the rolls.

'The overhead mixing'assenibly C comprises a pair of side support members 24) each'mounted on one of the vertical side supports '10 ofthe mill B. A- drawing roller 21 is mounted on a shaft '22 ro-tatably journalled between supports 20. A second drawing roller 23 is mounted on a shaft 24 rotatably journalled between a 'pairof pivot arms 2-5 eachp-ivotally mounted on supports 20. Shaft 22 is rotated'by means of a chain'26 passing about a sprocket 27 on shaft ZZ-and a 1sprocket 28- on the output shaft of a variable speed reducer 29 which is driven by a-motor 30. As the roller 21 is driven in the direction indicated in the drawings, the'band-18- ofelastomeric material is drawn between the rollers 21*and'23. Roller 23 is urged againsttheband -18 by the force-of gravity. A screw member 31 is mounted on a shaft 32 which is rotatably journalled between side supports 20, Screw member 31 is rotated in response-to rotation of roller 21 by means of a chain 33 trained about sprockets'34'and 35 mounted on shafts 22 and 32, respectively. Mounted between supports Zti, and parallelto screw member 31, is a guide rod 36. Slidably-mounted on guide rod 36 is a 3 screw follower member 37 engaged with an endless double reversing screw thread 38, formed in screw member 31, for movement in alternating opposite directions as screw member 31 is rotated. Rotatably mounted on the front of member 37 is a horizontal roller 39 by which the band 18 of elastomeric material is supported as it is drawn upward by the rollers 21 and 23. A pair of horizontal parallel rollers 40, each mounted on one of a pair of brackets 41 mounted on member 37, guide the lateral movement of the band 18 as member 37 moves from side to side.

The stock accumulating shaft assembly A includes a pair of horizontal parallel channel guide members 42 each mounted on the inner side of side supports below the drawing rolls 21 and 23 and screw member 31. A rectangular shelf 43, formed of a front angle member 44 and rear angle member 45 which support a horizontal plate 46, is slidably mounted in guide members 42. Also mounted on the inner sides of side supports 21! are a pair of double acting air cylinders 47, each having a piston 48 and piston rod 49. The outer end of each piston rod 49 is mounted on rear angle member 45 to thereby move shelf 43 as pistons 48 are moved in cylinders 17 by air directed thereto by a four-way spring return valve 50. Valve 59 is actuated in response to the contact of either of a pair of limit switches 51 and 52, mounted on side supports 20, by tripping fingers 53 and 54, respectively, which are mounted on the under side of screw follower member 37. Operation of the apparatus will be more clearly understood from the operating description which follows:

Machine Operation In the use of the shelf assembly A in cooperation with a roll mill B to uniformly mix elastomeric materials, the operator cuts the band 18 as it passes about mill roll 11 and throws the end of the band 18 over the horizontal roller 39 of the overhead mixer C, between the parallel rollers 40, to the bight of the drawing rollers 21 and 23.- The accumulating shelf is normally in the position shown in full line in FIG. 2, thereby interrupting the return of the band 18 to the rolling bank 19 of material above the bight of the milling rolls 11 and 12. The operator then adjusts the speed of drawing roller 21 to at least match that of the milling roll 11 by means of an adjusting handle 55 for the variable speed reducer 29. Thus, the band 18 is pulled directly from milling roll 11 by drawing rollers 21 and 23 without troublesome bagging or sagging. Screw member 31 turning in response to rotation of roller 21 causes follower member 37 to move from side to side distributing the band 18 over the width of shelf 43 in a folded or rolled condition, as at 56. As member 37 moves to the left as viewed in FIG. 1, finger 54 trips limit switch 52 causing electrical current to flow in a solenoid coil 57. Energization of coil 57 causes a piston rod 58 of valve 50 and its pistons 59 to move to their positions shown in phantom in FIG. 3 against the force of piston return spring 60. Air from supply line 61 thus flows through valve '50 and line 62 to one side of pistons 48 of cylinders 47, causing pistons 48 and shelf 43 to move to their positions shown in phantom in FIGS. 2 and 3, air from the opposite side of pistons 48 being exhausted through line 63 and valve 51) to exhaust line 64. As shelf 43 is so moved, a scraper member 65, rigidly mounted between side supports 20, causes the material at 56 to be scraped from the shelf onto the bight of the milling rolls 11 and 12. As member 37 reverses its direction finger 54 disengages limit switch 52 interrupting current to solenoid coil 57 and allowing piston rod 58 and pistons 59 of valve 50 to be returned to their positions shown in full line in FIG. 3. Air from supply line 61 is thus directed through line 63 to move the pistons 48 of cylinders 47 and shelf 43 to their positions shown in full line in FIGS. 2 and 3, air being exhausted from cylin ers 7 t gh 5 and valve 50 to exhaust 4 line 66. As member 37 moves to the right as viewed in FIG. 1, the band 18 again accumulates on shelf 43 to diminish the rolling bank 19. As member 37 approaches the extreme of its travel in this direction finger 53 contacts limit switch 51 to repeat the dumping cycle.

In the mixing of greater amounts of elastorneric material is may be necessary or desirable to allow member 37 to move the entire length of its travel and return before causing actuation of the accumulating assembly A, thus decreasing the size of the rolling bank 19 to a minimum. To accomplish this, either of the limit switches 51 or 52 may be removed from the circuit shown in PEG. 3. Thus, solenoid coil 57 would be actuated by but one of the fingers 53 or 54 on follower member 37.

The invention has been described with respect to one specific embodiment thereof as incorporated in a two roll mixing mill. It will be apparent to those skilled in the art to which it pertains however, that adaptations and modifications of the apparatus may readily be made and hence the invention is not limited to the construc tional details herein illustrated and described except as required by the spirit and scope of the appended claims.

Having thus described the invention, I claim:

1. Apparatus for increasing the uniformity of mixing of elastomeric material comprising, in combination with a roller mill having a pair of mixing rolls and an overhead mixer, a movably mounted material accumulating member normally in position to receive said material as it passes from said overhead mixer; and means to move said accumulating member from said position thereby allowing said material accumulated thereon to drop onto said mixing rolls.

2. Apparatus for increasing the uniformity of mixing of elastorncric material comprising, in combination with a roller mill having at least two mixing rolls and an overhead mixer; a material accumulating shelf movably mounted on said apparatus beneath said overhead mixer and above said mixing rolls; and means to move said shelf to and from a position for accumulating said material as it passes from said overhead mixer.

3. Apparatus for uniformly mixing elastomeric material comprising at least two parallel adjacent rolls for receiving and milling elastomeric material therebetween, means for receiving the elastomeric material after passage between said rolls and for directing it through a path spaced from said rolls for repassage therebetween, material accumulating means selectively positionable in said path to temporarily prevent passage of material to said rolls, and means responsive to passage of material in said path for periodically moving said material accumulating means to and from its material passage preventing position.

4. Apparatus for improving the uniformity of mixing of elastomeric material on a roller mill having at least two mixing rolls and an overhead mixer, comprising a horizontal material accumulating shelf, means slidably mounting said shelf on said apparatus for movement in a plane disposed between said overhead mixer and said mixing rolls, means to move said shelf to and from a position for receiving said material as it passes from said overhead mixer, and means to dislodge said material from said shelf as said shelf is moved from said position thereby allowing said material to be dumped onto said mixing rolls.

5. In an apparatus for improving the uniformity of mixing of elastomeric material on a roller mill having at least two contra-rotating mixing rolls, and an overhead mixer including a pair of material drawing rolls, an endless double reversing screw rotated in timed relationship to the speed of rotation of said mixing rolls, and a material guide carriage mov-ably engaged with said reversing screw to move said carriage in alternating opposite directions as said reversing screw is rotated; the improvement comprising a material accumulating shelf, means mounting said shelf on said apparatus for movement in a horizontal plane disposed between said drawing rollers and said mixing rolls, motive means operable to move said shelf to and from a position for receiving said material passing from said drawing rollers, means responsive to movement of said guide carriage in at least one direction to operate said motive means, and means to dislodge said material from said shelf as said shelf is moved from said position thereby allowing said material to fall onto said mixing rolls.

6. Apparatus for uniformly mixing elastomeric material, comprising at least two material mixing rolls movably mounted on said apparatus in generally axially parallel relationship, at least two material drawing rollers movably mounted on said apparatus, an endless double reversing screw rotatably mounted on said apparatus adjacent to said rollers and axially parallel thereto, a material guide carriage movably mounted on and engaged With said screw to move axially of said screw in alternating opposite directions as said screw is rotated and to guide material from said rolls to said rollers, a material accumulation shelf slidably mounted on said apparatus for movement in a horizontal plane disposed between said rolls and said rollers, motive means operable to move said shelf in said plane to and from a position for interrupting the passage of material passing from said rollers to said rolls, means to rotate said rolls in opposite directions to one another, means to rotate at least one of said rollers at a peripheral speed at least equal to the peripheral speed of said rolls, means responsive to rotation of said rollers to rotate said screw, means mounted on said apparatus adjacent at least one end of said screw engageable with said guide carriage to operate said motive means, and means to scrape said material from said shelf as the latter moves from said position.

References Cited in the file of this patent UNITED STATES PATENTS 1,736,582 Davidson NOV. 19, 1929 1,397,961 Snyder Feb. 14, 1933 2,593,282 Engler Apr. 15, 1952 2,973,549 Hurst Mar. 7, 1961 

2. APPARATUS FOR INCREASING THE UNIFORMITY OF MIXING OF ELASTOMERIC MATERIAL COMPRISING, IN COMBINATION WITH A ROLLER MILL HAVING AT LEAST TWO MIXING ROLLS AND AN OVERHEAD MIXER; A MATERIAL ACCUMULATING SHELF MOVABLY MOUNTED ON SAID APPARATUS BENEATH SAID OVERHEAD MIXER AND ABOVE SAID MIXING ROLLS; AND MEANS TO MOVE SAID SHELF TO AND FROM A POSITION FOR ACCUMULATING SAID MATERIAL AS IT PASSES FROM SAID OVERHEAD MIXER. 